Centrifugal compressor



July 31, 1945. K. D. MCMAHAN 2,380,772

CENTRIFUGAL COMPRES SOR Filed Sept. 1, 1943 2 Sheets-Sheet l Inventor: Kenton D. Mai/7am, by A "1 His Attorney July 31, 1945.. K. D. MOMAHAN 2,380,772

CENTRIFUGAL COMPRESSOR I Filed Sept. 1, 1943 2 Sheets-Sheet 2 Fig. 3.

Inventor: Kenton D. Mo Mahan,

b9 JV His ttorneg.

Patented July 31', 1945 CENTBIFUGAL COMPRESSOR Kenton D. McMahan, Scotla, N. Y., aasignor to General Electric Company, a corporation of New York Application September 1, 1943, Serial No. 500,813

I 2 Claims. (Cl. 230-132) The present inventionerelates to centrifugal compressors. I It is well adapted for incorporation in centrifugal compressors designed for use as superchargers for aircraft internal combustion engines and it is this application of my invention which I have elected to specifically illustrate and describe. It is .to be understood, however, that thisis only by way of example.

The object of my invention is to provide an improved construction and arrangement in a centrifugal compressor, and for a consideration of what I believe to be novel and my invention, attention is directed to the following specification and to the claims appended thereto.

In the drawings, Fig. 1 is a sectional view of a centrifugal compressor embodying my invention; Fig. 2 is a detail view on a larger scale taken on line 2-2, Fig. 1, and Fig. 3 is a view similar to Fig. 1 of another embodiment of my invention.

Referring to the drawings, Figs. 1 and 2, tindicates a shaft of a centrifugal compressor which may be carried in suitable bearings, not shown. Mounted on shaft l is the impeller 2 of the compressor, the vanes of the impeller being indicated at 3. It may be attached to the shaft in any suitable manner. Surrounding shaft l adjacent the inlet of the impeller are walls which define an annular chamber 4 from which air is supplied to the impeller, air being supplied to the chamber through a conduit 5. In the case of an aircraft engine, conduit 5 may connect through a pipe line with a suitable ram which faces into the slip stream of the aircraft so as to take air from the slip stream of the aircraft as is now known.

Surrounding the impeller is a diffuser comprising side walls 6 and 1 between which are located curved diffuser vanes 3 which define between them diffuser passages 9 through which air flows in the directionindicated by the arrows A. Passages 9 are shaped to convert velocity into pressure as is well understood in connection with centrifugal compressors of this type.

The construction so far described is a known 1 one andis to be taken as typical of any suitable construction of centrifugal compressor. In the case of an aaircraft internal combustion engine, haft I may be connected to the engine shaft through suitable gearing, the impeller being driven from the engine.

In operation, air is discharged by the impeller to the inlet ends of the diffuser passages and is directed by the difiuser vanes 8 through the passages to the discharge ends thereof. The air discharged from the passages has a rotational component as is indicated by the arrows A. It is discharged from the diffuser passages at relatively high velocity and flows in the form of a vortex.

According to my invention, instead of providing the usual annular scroll into which the air from the passages between the diffuser vanes 8 is discharged, I provide walls located in the region of the discharge ends of vanes 8 which define an annular vortex chamber III, which vortex chamber is connected by an annular passage H to an annular discharge chamber l2, and in passage I i I provide curved vanes I3 which define between them diffuser passages N the entrance ends of which face against the direction o flo in chamber ill and through which air flows from the annular vortex chamber it to the annular discharge chamber i2. Annular discharge chamber 62 is defined by suitable walls which form parts of the compressor casing. The purpose of the difi'user passages it, which form what may be termed a secondary difluser, is to supplement the difiuser formed by th difiuser passages 9 which form what may be termed a primary difiuser, in converting velocity head into static head, and to completely stop the rotational component of velocity of the air discharged from the difiuser passages ii. In operation, the air from difluser passages 9 is discharged into vortex chamber it]! at relatively high velocity and in a generally cirular direction. The radial inner ends of vanes iii of the secondary difiuser catch or "pick ed the peripheral portion of the air flowing in vortex chamber Ill, directing it through the diffuser passages It to the annular discharge chber it. The secondary diffuser vanes "pick off only the high potential flow of the vortex and cause the low potential flow to return past the primary diffuser jets to be accelerated by such jets before it is picked oil by the vanes. The air that enters the passages M of the secondary difiuser is further reduced in velocity and turned in a radial direction. Thus a substantial portion of l the velocity head entering the vanes is recovered as pressure which would otherwise have been lost as turbulence in the casing.

It has been found that a mere lengthening of the passages of the primary diffuser beyond av fixed length reduces rather than increases the primary diffuser to define a primary diffuser discharge chamber. It serves to direct all discharged from the primary diffuser axially into vortex chamber I0, thus imparting to the air an axial flow component. Air directed from the primary diffuser into vortex chamber III has, as

pointed out above, a substantial circumferential component causing it to tend to flow circumferentially around the chamber. The resultant is flow in chamber I! in the form of a vortex havin both a circumferential and an axial component. The radially outer portion of this vortex flow, which is the high potential portion of the flow, is picked oil by the secondary difluser. The radially inner portion, which represents the lower potential flow, is caused to return past the Jets of air discharging from the primary diffuser to be accelerated by such jets before it is picked off by the vanes of the secondary diffuser.

The air issuing from the secondary diifuser, its rotational component of velocity being reduced to zero, enters annular discharge chamber I: in a generally radial direction. Leading from chamber l2 are a number of discharge openings H which may lead to any suitable point or points of consumption. For example, in the case of a radial type internal combustion engine, they may be connected with the several engine cylinders.

If desired, the vanes I! of the secondary diffuser may be made hollow and a suitable coolant circulated through them for cooling the air flowing through the diffuser passages ll. Such vanes are shown in Figs. 1 and 2, the passages it through the vanes l3 being connected to passages I8 and 20 for circulation of coolant through them.

In Fig. 3, my invention is shown as being embodied in a two-stage centrifugal compressor, the secondary diifuser being located between the two stages. In this figure, parts corresponding to those of Figs. 1 and 2am designated by the same reference characters with the exponent a added. The air from chamber l2 flows by way of passage I! to the inlet of the second stage impeller 22 from which it is discharged through the second stage difluser 23 to a discharge chamber 24.

What I claim as new and desire to secure by Letters Patent of the Umted States is:

1. A centrifugal compressor comprising an impeller, a primary diffuser surrounding the impeller, a wall which surrounds the discharge end of the primary diffuser to define a primary diffuser discharge chamber having an annular axially facing discharge opening, a wall which defines an annular vortex chamber axially displaced with respect to said discharge chamber and with which said axially facing discharge opening communicates for flow of gas from the primary diffuser discharge chamber to said vortex chamber whereby flow in said vortex chamber is in the form of a vortex having both a circumferential and an axial component, walls which define a discharge chamber which surrounds said vortex chamber, and secondary diffuser vanes which deflne diffuser Passages the inlet ends of which communicate with the peripheral portion of said vortex chamber and the exit ends of which communicate with said surrounding discharge chamber whereby said vanes serve to continuously pick off the peripheral portion of the vortex flow in the vortex chamber and direct it to the discharge chamber.

2. A centrifugal compressor comprising an impeller, a primary diffuser surrounding the imeiler, a wall which surrounds the discharge end of the primary dlfluser to define a primary diffuser discharge chamber, walls which define a vortex chamber which is at least in part axially displaced with respect to said discharge chamber, walls which define an annular passage which connects the primary diffuser discharge chamber to the'vortex chamber at one side of its center whereby gas flowing from the said discharge chamber to we vortex chamber has both an axial and a circumferential component of flow to set up flow in the vortex chamber in the form of a 'vortex having both a, circumferential and an KENTON D. MCMAHAN. 

